Force and Motion
NEWTON'S LAWS OF MOTION
mass of the earth (5.95 x 10 kg)
mass of the object
radius of the earth (6.367 x 10 m)
The mass (m ) of the object cancels, and the value of (g) can be determined as follows
since a=g by substituting (g) for (a) in the previous equation.
If the object is a significant distance from the earth, we can demonstrate that (g) is not a
constant value but varies with the distance (altitude) from the earth. If the object is at an
altitude of 30 km (18.63 mi), then the value of (g) is as follows:
As you can see, a height of 30 km only changes (g) from 9.8 m/sec to 9.7 m/sec . There
will be an even smaller change for objects closer to the earth. Therefore, (g) is normally
considered a constant value since most calculations involve objects close to the surface
of the earth.